svn commit: r268310 - head/libexec/rtld-elf/arm

[Nathan Whitehorn]

Thank you! I can now upgrade my AVILA for the first time in 3 years. 
Most things seem to work fine, despite the long absence.
-Nathan

On 07/06/14 03:24, Andrew Turner wrote:
> Author: andrew
> Date: Sun Jul  6 10:24:06 2014
> New Revision: 268310
> URL: http://svnweb.freebsd.org/changeset/base/268310
>
> Log:
>    Align the stack in _rtld_bind_start. Normally this is called with the
>    correct stack alignment, however when we have a leaf function that uses
>    thread local storage it calls __aeabi_read_tp to get the thread pointer.
>    Neither GCC or clang see this as a function call so will align the stack
>    to a 4-byte boundary. This may be a problem as _rtld_bind expects to be
>    on an 8-byte boundary.
>    
>    The solution is to store a copy of the stack pointer and force the
>    alignment before calling _rtld_bind.
>    
>    This fixes a problem with armeb where applications would crash in odd ways.
>    It should also remove the need for a local patch to clang to force the
>    stack alignment to an 8-byte boundary, even for leaf functions. Further
>    testing will be needed before reverting this local change to clang as we
>    may rely on it in other places.
>    
>    Reviewed by:	jmg@
>
> Modified:
>    head/libexec/rtld-elf/arm/rtld_start.S
>
> Modified: head/libexec/rtld-elf/arm/rtld_start.S
> ==============================================================================
> --- head/libexec/rtld-elf/arm/rtld_start.S	Sun Jul  6 07:34:18 2014	(r268309)
> +++ head/libexec/rtld-elf/arm/rtld_start.S	Sun Jul  6 10:24:06 2014	(r268310)
> @@ -77,7 +77,7 @@ __FBSDID("$FreeBSD$");
>    *	lr = &GOT[2]
>    */
>   _rtld_bind_start:
> -	stmdb	sp!,{r0-r4,sl,fp}
> +	stmdb	sp!,{r0-r5,sl,fp}
>   
>   	sub	r1, ip, lr		/* r1 = 4 * (n + 1) */
>   	sub	r1, r1, #4		/* r1 = 4 * n */
> @@ -86,11 +86,14 @@ _rtld_bind_start:
>   	ldr	r0, [lr, #-4]		/* get obj ptr from GOT[1] */
>   	mov	r4, ip			/* save GOT location */
>   
> +	mov	r5, sp			/* Save the stack pointer */
> +	bic	sp, sp, #7		/* Align the stack pointer */
>   	bl	_rtld_bind		/* Call the binder */
> +	mov	sp, r5			/* Restore the old stack pointer */
>   
>   	str	r0, [r4]		/* save address in GOT */
>   	mov	ip, r0			/* save new address */
>   
> -	ldmia	sp!,{r0-r4,sl,fp,lr}	/* restore the stack */
> +	ldmia	sp!,{r0-r5,sl,fp,lr}	/* restore the stack */
>   	mov	pc, ip			/* jump to the new address */
>   
>